1. Field of the Invention
The present invention relates to an optical transceiver that time-multiplexes an inputted electric signal, converts the electric signal into a light signal, and output the converted signal, and that converts an input light signal into an electric signal, demultiplexes the light signal, and output the demultiplexes signal. In addition, the invention relates to a multiplexing integrated circuit, a demultiplexing integrated circuit, an integral multiplexing/demultiplexing integrated circuit, which are used for the optical transceiver, and a method for evaluating and testing the optical transceiver.
2. Description of Related Art
FIG. 19 is a block diagram illustrating a configuration of a typical high-speed optical transmitter-receiver (hereinafter referred to just as a “transceiver”), which is shown in, for example, a document, “MUX/DEMUX built-in 3.3V operation 2.5 Gbit/s optical transceiver” by Suzuki, and others, 1998, The Institute of Electronics, Information and Communication Engineers, Society meeting, preprints B-10-70, P392. In FIG. 19, a reference numeral 1 denotes an optical transceiver; 2 denotes a low-speed parallel input interface (I/F) for receiving a parallel data signal inputted from outside of the optical transceiver 1; 3, a multiplexing circuit (MUX) for time-multiplexing the parallel data signal inputted to the optical transceiver 1; 4, an electricity-light converter (E/O) for converting an output electric signal of the multiplexing circuit 3 into a light signal; 5, a transmitting unit comprising the multiplexing circuit 3 and the electricity-light converter 4; 6, a transmitting side path (TX) comprising the low-speed parallel input interface 2 and the transmitting unit 5.
In addition, in FIG. 19, reference numeral 7 denotes a light-electricity converter (O/E) for converting a light signal, which is inputted from outside, into an electric signal; 8 denotes a demultiplexing circuit (DEMUX) for demultiplexing an output signal of the light-electricity converter 7; 9, a receiving unit comprising the light-electricity converter 7 and the demultiplexing circuit 8; 10, a low-speed parallel output interface (I/F) for outputting an output parallel signal of the demultiplexing circuit 8 to outside; 11, a receiving side path (RX) comprising the low-speed parallel output interface 10 and the receiving unit 9.
FIGS. 20, 21, and 22 are diagrams illustrating first, second, and third methods for evaluating and testing the optical transceiver 1 respectively. However, components inside the optical transceiver 1 are omitted. In FIGS. 20, 21, and 22, reference numeral 12 denotes an optical transceiver implemented substrate on which the optical transceiver 1 is placed; 13 denotes input electric wiring on the optical transceiver implemented substrate 12, which is used for inputting a parallel electric signal from outside to the low-speed parallel input interface 2 of the optical transceiver 1; 14 denotes output electric wiring on the optical transceiver implemented substrate 12, which is used for outputting an output parallel signal from the optical transceiver 1 to outside of the optical transceiver implemented substrate 12.
In addition, in FIGS. 20, 21, and 22, reference numeral 15 denotes a first optical fiber for outputting a light signal from the transmitting unit 5; 16 denotes a second optical fiber for inputting a light signal to the receiving unit 9; 17, a light measuring instrument that has a pseudo-random pattern generating function (PN_G) and a pseudo-random pattern detecting function (PN_C); 18, an electric measuring instrument that has a pseudo-random pattern generating function (PN_G) and a pseudo-random pattern detecting function (PN_C); 19, a loopback optical fiber that loops back a light signal, which is output from the transmitting unit 5, to the receiving unit 9; 20, a loopback electric wiring on the optical transceiver implemented substrate 12, which is used for looping back an output signal of the low-speed parallel output interface 10 to the low-speed parallel input interface 2.
Next, operation will be described.
In the first place, operation of the optical transceiver 1 will be described with reference to FIG. 19. A first parallel electric signal from outside is inputted to the optical transceiver 1 through the low-speed parallel input interface 2. The multiplexing circuit 3 time-multiplexes the inputted parallel electric signal to generate a first high-speed serial signal. The electricity-light converter 4 converts the first high-speed serial signal into a light signal, which is output to outside.
A high-speed serial light signal, which is inputted from outside, is converted into a second high-speed serial electric signal in the light-electricity converter 7. The demultiplexing circuit 8 segregates the second high-speed serial electric signal by time to generate a second low-speed parallel signal. The second low speed parallel signal is output to outside of the optical transceiver 1 through the low-speed parallel output interface 10.
Next, a first method for evaluation and testing shown in FIG. 20 will be described. A first pseudo-random pattern signal (hereinafter referred to as PN pattern signal), which is generated by the PN_G of the electric measuring instrument 18, is inputted to the optical transceiver 1 through the input electric wiring 13. After the PN pattern signal is converted into a light signal by the transmitting unit 5, the PN pattern signal is inputted to the light measuring instrument 17 through the first optical fiber 15. Evaluation and testing as to whether or not malfunction has occurred in the transmitting side path 6 is performed by checking whether or not there is an error of the first PN pattern signal, which has been inputted from the optical transceiver 1, using the PN_C of the light measuring instrument 17.
In a similar manner, the second PN pattern signal, which is generated by the PN_G of the light measuring instrument 17, is inputted to the optical transceiver 1 through the second optical fiber 16. After the second PN pattern signal is converted into an electric signal by the receiving unit 9, the second PN pattern signal is inputted to the electric measuring instrument 18 through the output electric wiring 14. Evaluation and testing as to whether or not malfunction has occurred in the receiving side path 11 is performed by checking whether or not there is an error of the second PN pattern signal, which has been inputted from the optical transceiver 1, using the PN_C of the electric measuring instrument 18.
Next, a second method for evaluation and testing shown in FIG. 21 will be described. A PN pattern signal, which is generated by the PN_G of the electric measuring instrument 18, is inputted to the optical transceiver 1 through the input electric wiring 13. Then, the PN pattern signal is converted into a light signal in the transmitting unit 5, and is output. This light signal is inputted to the receiving unit 9 through the loopback optical fiber 19. After the light signal is converted into an electric signal, the electric signal is inputted to the electric measuring instrument 18 through the output electric wiring 14. Evaluation and testing of malfunction, which cover both of the transmitting side path 6 and the receiving side path 11 of the optical transceiver 1 (that is to say, the whole optical transceiver 1 including the optical fiber path and the optical transceiver implemented substrate 12), are performed at a time by checking whether or not there is an error of the inputted PN pattern signal using the PN_C of the electric measuring instrument 18.
Next, a third method for evaluation and testing shown in FIG. 22 will be described. A PN pattern signal, which is generated by the PN_G of the light measuring instrument 17, is inputted to the optical transceiver 1 through the second optical fiber 16. Then, the PN pattern signal is converted into an electric signal in the receiving unit 9. The electric signal is inputted to the low-speed parallel input interface 2 through the loopback electric wiring 20. After the electric signal is converted into a light signal in transmitting unit 5, the light signal is inputted to the light measuring instrument 17 through the first optical fiber 15. Evaluation and testing of malfunction, which cover both of the receiving side path 11 and the transmitting side path 6 (that is to say, the whole optical transceiver 1 including an evaluation/test system and the optical transceiver implemented substrate 12), are performed at a time by checking whether or not there is an error of the inputted PN pattern signal using the PN_C of the light measuring instrument 17.
Because the conventional optical transceiver, and the method for evaluating and testing the conventional optical transceiver, were devised and embodied as described above, there was the following problem: although it is possible to evaluate and test the whole transmitting side path 6, the whole receiving side path 11, or the whole optical transceiver 1 as a whole, it is not possible to identify a path in the optical transceiver implemented substrate 12 and the optical transceiver 1 if malfunction occurs.
In addition, the conventional method for evaluation and testing produced the following problem: one or two measuring instruments, such as the light measuring instrument 17 and the electric measuring instrument 18, are used, which causes the evaluation/test system to become large.